유튜브(Youtube) 이미지 주소

Suppose that you want to do a screenshot of the following video:
https://www.youtube.com/watch?v=9kaCAbIXuyg

There is a little trick:

So your screenshot will be:
http://i.ytimg.com/vi/9kaCAbIXuyg/0.jpg                  (screenshot)
https://img.youtube.com/vi/9kaCAbIXuyg/0.jpg

if you want a thumbnail you can write the following:
http://i.ytimg.com/vi/9kaCAbIXuyg/1.jpg                  (thumbnail 1)
http://i.ytimg.com/vi/9kaCAbIXuyg/2.jpg                  (thumbnail 2)
http://i.ytimg.com/vi/9kaCAbIXuyg/3.jpg                  (thumbnail 3)
https://img.youtube.com/vi/9kaCAbIXuyg/1.jpg
https://img.youtube.com/vi/9kaCAbIXuyg/2.jpg
https://img.youtube.com/vi/9kaCAbIXuyg/3.jpg

the default thumbnail is the following:
http://i.ytimg.com/vi/9kaCAbIXuyg/default.jpg
https://img.youtube.com/vi/9kaCAbIXuyg/default.jpg

For the high quality version of the thumbnail use a url similar to this
http://i.ytimg.com/vi/9kaCAbIXuyg/hqdefault.jpg
https://img.youtube.com/vi/9kaCAbIXuyg/hqdefault.jpg

for a medium quality version of the thumbnail, using a url similar to the HQ:
http://i.ytimg.com/vi/9kaCAbIXuyg/mqdefault.jpg
https://img.youtube.com/vi/9kaCAbIXuyg/sddefault.jpg

For the maximum resolution version of the thumbnail use a url similar to this:
http://i.ytimg.com/vi/9kaCAbIXuyg/maxresdefault.jpg
https://img.youtube.com/vi/9kaCAbIXuyg/maxresdefault.jpg